Differences in the functional responses of two cell lines each expressing Pi-hydrolysis-coupled muscarinic receptors

• Published in: Neurochemical research Vol. 17; no. 4; pp. 375 - 379
• Main Authors: Baumgold, J, Paek, R
• Format: Journal Article
• Language: English
• Published: United States 01-04-1992
• Subjects: Calcium - metabolism; Cell Line; Fluorescent Dyes; Fura-2 - analogs & derivatives; Humans; Hydrolysis; Isoxazoles; Membrane Potentials - physiology; Protein Kinase C - physiology; Receptors, Muscarinic - metabolism; Tumor Cells, Cultured
• ISSN: 0364-3190; 1573-6903
• DOI: 10.1007/BF00974580

Fluorescent oxonol dyes were used to measure changes in the membrane potential of two different cell lines each expressing Pi-hydrolysis coupled muscarinic receptors. Both SK-N-SH human neuroblastoma cells and m1-transfected A9 L cells express muscarinic receptors which, when stimulated, elicit a large increase in intracellular calcium, and release of inositol phosphates. Despite the similarity in this second-messenger response, muscarinic stimulation resulted in a hyperpolarization in the transfected A9 L cells whereas a small depolarization was observed in the neuroblastoma cells. The carbachol-mediated hyperpolarization of the transfected A9 L cells could be mimicked by increasing intracellular calcium with the ionophore A23187, suggesting that it may be mediated by calcium-activated potassium channels. Exposure of SK-N-SH cells to A23187, on the other hand, had no effect on the membrane potential. These studies demonstrate that the activation of a second messenger system does not solely dictate the electrophysiological response of a cell, but that other factors such as the expression of ion-channels is critical in the determination of that response.